JPH0429814B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application) The present invention relates to an improvement of a hydraulic circuit in a construction machine such as a hydraulic excavator.

(Prior art) When operating other actuators while the construction machine is running, in a conventional hydraulic excavator, all directional control valves are connected in parallel, as shown in the hydraulic circuit in Figure 1, so the actuator with a light load is operated. The amount of oil supplied to the traveling motor that has been activated is less than the amount of oil supplied to the other traveling motor, causing meandering. Another problem is that even if an attempt is made to operate another actuator whose load pressure is higher than that of the travel motor while the vehicle is running, that actuator will not operate.

To explain in more detail the conventional circuit diagram shown in FIG. 1, 1 is a first hydraulic pump, 2 is a second hydraulic pump, and 3 is a prime mover that drives the first and second hydraulic pumps. Reference numeral 4 designates a first group of directional control valves, which are connected in random order, one for left and right travel, for example, a left travel directional control valve 4a, a bucket directional control valve 4b, a first boom directional control valve 4c, and a relief valve. It is composed of 4d. Reference numeral 5 denotes a second group of directional control valves connected in parallel in random order for left and right travel, for example, a right-hand travel directional control valve 5a, a second boom directional control valve 5b, a swing directional control valve 5c, and an arm control valve. It is composed of a directional switching valve 5d and a relief valve 5e.

The hydraulic circuit configured as described above has the following problems listed in A) to D) below.

A When operating the arm while driving straight (operating the left-hand direction switching valve 4a and the right-hand direction change-over valve 5a in the same direction), what are the arm directional control valve 5d and the right-hand direction change-over valve 5a? Because of the parallel connection, in the relationship of arm movement pressure<traveling drive pressure, pressure oil tends to flow to the arm directional switching valve 5d side, which has a lighter load compared to the right traveling directional switching valve 5a side. As a result, the right travel motor speed becomes slower than the left travel motor speed, and although the arm moves, it cannot travel straight. If arm movement pressure>traveling drive pressure, the pressure applied to the arm cylinder is insufficient, so even if the vehicle can travel straight, the arm will not move.

B When performing a turning operation while traveling straight, the right direction switching valve 5a and the turning direction switching valve 5c are connected in parallel, so in the case of the relationship of turning drive pressure < running drive pressure, the right direction switching valve 5a and the turning direction switching valve 5c are connected in parallel. Switching valve 5
Pressure oil tends to flow toward the turning direction switching valve 5c side compared to the side a. As a result, the speed of the right travel motor becomes slower than the left travel motor speed, and although the vehicle can turn, it is unable to travel straight. In addition, if swing drive pressure>travel drive pressure, the pressure applied to the swing motor is insufficient, making it difficult to perform a swing operation.

C When performing a bucket operation while traveling straight, the left running directional control valve 4a and the bucket directional control valve 4
Since b is connected in parallel, if the relationship is bucket driving pressure < travel driving pressure, pressure oil flows to the bucket directional switching valve 4b side, which has a lighter load compared to the left traveling directional switching valve 4a side. It becomes a trend. As a result, the left travel motor speed becomes slower than the right travel motor speed, and although the bucket moves, it cannot travel straight. If the bucket drive pressure is greater than the running drive pressure, the pressure applied to the bucket cylinder is insufficient and the bucket does not move even if the vehicle can travel straight.

D When operating the boom while traveling straight, the left travel direction switching valve 4a and the first boom direction switching valve 4c
In addition, since the right running directional switching valve 5a and the second boom directional switching valve 5b are each connected in parallel, in the case of the relationship of boom driving pressure < running driving pressure, the first, light-loaded directional switching valve 5a and the second boom directional switching valve 5b are connected in parallel. Pressure oil tends to flow into the second boom directional control valves 4c and 5b, and the boom moves, but cannot travel. Furthermore, in the relationship of boom drive pressure>travel drive pressure, the pressure applied to the boom cylinder is insufficient, and even if the boom can travel straight, the boom will not move.

(Objective of the Invention) The present invention has been made in order to solve the problems of the prior art described above, and is capable of maintaining straight traveling even when other actuators are activated while driving, and also ensuring that other actuators can also be activated. The goal is to provide a circuit that can

(Structure of the Invention) Among the plurality of directional switching valve groups that control the direction of pressure oil of the actuator, the first directional switching valve group 4 includes one of the left and right running directional switching valves 4a, A bucket directional control valve 4b, a first boom directional control valve 4c, etc. are connected in parallel in random order, and a throttle 4f and a check valve 4 are connected to the parallel passage connected to the traveling direction control valve 4a.
e are provided in series, and the second group 5 of directional control valves includes the other one of the left and right running directional control valves 5a, and the second boom directional control valve 5.
b. The turning directional switching valve 5c, the arm directional switching valve 5d, etc. are connected in parallel in random order, and a throttle 5g and a check valve 5f are provided in series in the parallel passage connected to the traveling directional switching valve 5a.

In addition, in the first state of the switching valve 6, the first hydraulic pump 1 is connected to one of the traveling directional switching valves 4a via the most upstream main pressure oil inlet of the first directional switching valve group 4 and the switching valve 6. and the check valve 4e, and the second hydraulic pump is connected to the other travel direction switching valve 5a.
and the check valve 5f, and via the switching valve 6 to the most upstream main pressure oil inlet of the group 5 of the second directional switching valves.

In the second state in which the switching valve 6 is switched, the first hydraulic pump 1 is connected to the second hydraulic pump 1 through the most upstream main pressure oil inlet of the first directional switching valve group 4 and the switching valve 6. The second hydraulic pump 2 is connected between the traveling direction switching valve 5a of the directional switching valve group 5 and the check valve 5f, and the running direction of the first directional switching valve group 4 is switched via the switching valve 6. It is configured to be switchably connected between the valve 4a and the check valve 4e and to the most upstream main pressure oil inlet of the group 5 of the second directional switching valves.

Further, each of the traveling direction switching valves 4a, 5a is provided with an auxiliary switching valve 4a', 5a' which is linked to the travel direction switching valve 4a, 5a, and the directional switching valve 4b, 4c, 5c, 5d for an actuator that requires independence from traveling is provided with an auxiliary switching valve 4a', 5a'. When auxiliary switching valves 4b', 4c', 5c', and 5d' are provided which operate in conjunction with the switching valves, and at least one actuator that requires running and independence is operated during straight-ahead running, the switching valve 6 is The auxiliary switching valve 4b' is connected to the pilot port.
The switching valve 6 is automatically switched by applying pilot pressure or reducing the pressure via terminals 4c', 5c', and 5d'.

(Example) Examples of the hydraulic circuit of the present invention will be described below.

Fig. 2 is a hydraulic circuit diagram showing a first embodiment of the present invention, Fig. 3 is a hydraulic circuit diagram showing a second embodiment of the invention, and Fig. 4 is a hydraulic circuit diagram showing a third embodiment. , FIG. 5 shows a part of the hydraulic circuit of another embodiment in which the passage of the switching valve is partially exposed outside. In these figures, the same components as those shown in FIG. 1 are designated by the same reference numerals.

Now, in the embodiment shown in FIG. 2, 1 is a first hydraulic pump, 2 is a second hydraulic pump, and 3 is a prime mover that drives the first and second hydraulic pumps. Reference numeral 4 denotes a first directional switching valve group, which is composed of one for left and right travel, for example, a left running directional switching valve 4a, a bucket directional switching valve 4b, and a first boom directional switching valve 4c. And these directional control valves 4a~
4c are connected in parallel to each other, and auxiliary switching valves 4a' to 4c' are connected to each of the switching valves 4a to 4c, respectively. Reference numeral 5 denotes a second group of directional control valves, the other for left and right travel, for example, a directional control valve for right travel 5a, a second directional control valve for boom 5b, a directional control valve for swing 5c, and a directional control valve for arm 5d. The directional control valves 5a to 5d are connected in parallel to each other, and among the directional control valves 5a to 5d, the directional control valve 5b
Each of the switching valves except the one shown in FIG. 4e
4f is a check valve provided in the parallel passage of the left travel directional control valve 4a, and 4f is a throttle provided in series with the check valve 4e.

5f is a check valve provided in a parallel passage of the right travel direction switching valve 5a, and 5g is a throttle provided in series with the check valve 5f. Reference numeral 6 denotes a switching valve, which connects the check valve 4e and the left running directional switching valve 4a with the first hydraulic pump 1 and the main pressure oil inflow of the group 5 of the second directional switching valve. It is provided in the middle of the pipe line 11. Reference numeral 8 denotes a main pressure oil inflow pipe of group 4 of the first directional switching valve branched from the front stage of the switching valve 6.

12 is a check valve 5f and a right-hand travel direction switching valve 5
This is a pipe line that connects the second hydraulic pump 2 and the second hydraulic pump 2. Reference numerals 9 and 10 are relief valves that regulate the maximum pressure of the first and second hydraulic pumps, respectively. 13 is a pilot pump, 14 is a relief valve that regulates the maximum pressure of the pilot pump 13, and 15 is an auxiliary switching valve 5a' that operates in conjunction with the right-hand travel directional switching valve 5a, and a pilot pipe that guides the pressure oil of the pilot pump 13. , 16 are drain pipes of the auxiliary switching valve 5a'. Reference numerals 17 and 18 refer to an auxiliary switching valve 5a' and an auxiliary switching valve 4 that operates in conjunction with the left travel direction switching valve 4a.
The pilot pipe connected to a', 19 is the auxiliary switching valve 4
20 is a pilot pipe connecting the auxiliary switching valve 4a' and the pilot port of the switching valve 6; 21 is a pilot pipe branching from the pilot pipe 20 and connecting the directional switching valves 4a, 5a; The auxiliary switching valves are connected to one of the auxiliary switching valves 4b', 4c', 5c', and 5d' except for the auxiliary switching valves 4a' and 5a' that operate in conjunction with the pilot pipes 22, 23, and 2.
4 in random order, and the final stage auxiliary switching valve is connected to the drain pipe 25.

Therefore, the pilot conduit 15 is operated when the traveling direction switching valves 4a, 5a are in the neutral position or only one of them is in the operating position, and when the traveling direction switching valve 4
a, 5a are in the operating position, and the other actuator directional control valves 4b, 4c, 5c, 5d are all in the neutral position, the water is drained to the tank via any of the drain pipes 16, 19, 25. Since it is connected, pilot pressure does not act on the switching valve 6.
Only when both the traveling directional control valves 4a and 5a are in the operating position and at least one of the directional control valves for other actuators is in the operating position, the drain pipe is shut off and the pilot port of the switching valve 6 is connected. It is constructed so that pilot pressure acts on it.

Next, the configuration of the switching valve 6 will be explained.

A When the switching valve 6 is in the A position, the first hydraulic pump 1 is connected to the pipe line 8 branched from the stage before the switching valve 6.
It is connected to the main pressure oil inflow pipe of the first directional switching valve group 4 through the switching valve 6 and the pipe 7 between the check valve 4e and the left running directional switching valve 4a. has been done. The second hydraulic pump 2 is connected between the right travel direction switching valve 5a and the check valve 5f via a pipe line 12 branched from the front stage of the switching valve 6, and is also connected to the pipe line 11 via the switching valve 6. through second directional valve group 5
is connected to the main pressure oil inflow pipe. That is, the pressure oil of the first hydraulic pump 1 is supplied to the first group 4 of directional valves, and the pressure oil of the second hydraulic pump 2 is supplied to the group 5 of directional valves.

(b) Next, when the switching valve 6 is in the (b) position, the first hydraulic pump 1 is connected to the main pressure oil inflow pipe of the first directional switching valve group 4 via a pipe line 8 branched from the stage before the switching valve 6. At the same time, it is connected to the main pressure oil inflow pipe of the second directional switching valve group via the pipe 11 via the switching valve. Further, the second hydraulic pump 2 is connected to a pipe line 12 branched from the front stage of the switching valve 6.
through the right travel directional control valve 5a and check valve 5.
It is connected between the left travel direction changeover valve 4a and the check valve 4e via the changeover valve 6 and the conduit 7. That is, the pressure oil of the first hydraulic pump 1 is supplied in parallel to the main pressure oil inflow pipes of the first and second directional control valve groups 4 and 5, and the pressure oil of the second hydraulic pump 2 is supplied to the left and right travels. directional control valves 4a and 5a, respectively.

(Operation of the first embodiment) At no load: In the state shown in FIG. 2, that is, in a state in which no operation is performed, the pressure oil of the first hydraulic pump 1 passes through the pipe 8 and flows through the first directional control valve. Return to the tank via the group 4 center bypass passage. Similarly, the pressure oil of the second hydraulic pump 2 passes through the conduit 11 via the switching valve 6 to the second hydraulic pump 2.
It returns to the tank via the center bus pass passage of group 5 of the directional control valves. In addition, the pressure oil of the pilot pump 13 passes through the pilot pipe 15 and is connected to the auxiliary valve 5.
a' and returns to the tank via drain line 16. In other words, it constitutes a no-load circuit similar to a conventional hydraulic circuit.

When activated: A When traveling only in a straight line: Directional switching valve 4 for left travel
When a is switched to position A (or position B) and the right travel direction switching valve 5a is switched to position A (or position B), the auxiliary switching valve 4 is
a'5a' are also switched to the A' position, and the pressure oil from the pilot pump 13 is transferred to the pilot pipe 15→
Auxiliary switching valve 5a' → Pipe 17 (Pipe 18) → Auxiliary switching valve 4a' → Pilot pipes 20, 21 → Auxiliary switching valve 4b' → Pilot pipe 22 → Auxiliary switching valve 4c' → Pilot pipe 23 → Auxiliary switching valve 5d'→
The water is guided from the pilot pipe 24 to the drain pipe 25 via the auxiliary switching valve 5c' and returns to the tank. Therefore, the pressure in the pilot line 20 becomes almost zero, and the switching valve 6 maintains the position A in FIG. The pressure oil led to line 7 goes directly to the left travel directional control valve 4a, and the pressure oil led to line 8 goes from parallel passage to throttle 4f to check valve 4.
It is supplied to the left travel directional switching valve 4a via e. That is, the entire amount of pressure oil from the first hydraulic pump 1 is supplied to the left travel motor.

Moreover, the pressure oil of the second hydraulic pump 2 is supplied to the pipes 11 and 1.
The pressure oil distributed to 2 and led to the pipe 11 passes through the parallel passage → throttle 5g → check valve 5f to the right-hand travel direction switching valve 5a, and the pressure oil led to the pipe 12 goes directly to the right-hand travel. It is supplied to the directional switching valve 5a. That is, since the entire amount of pressure oil from the second hydraulic pump 2 is supplied to the right travel motor, if the first and second hydraulic pumps 1 and 2 have the same capacity, the vehicle will travel straight.

B When operating another actuator that requires independence during the above operation (while traveling straight) (for the sake of explanation, we will explain the operation when the arm is operated) If the arm directional control valve 5d is switched while traveling straight The auxiliary switching valve 5d' is also switched in conjunction, the pilot lines 23 and 24 are cut off, and the pressure of the pilot line 20 is increased to the regulated pressure of the relief valve 14.
This pressure acts on the pilot port of the switching valve 6, and the switching valve 6 is automatically switched to the ``ro'' position. Therefore, the pressure oil of the first hydraulic pump is switched and connected to pipes 8 and 11, and the pressure oil led to pipe 8 is switched to the left running direction via the parallel passage → throttle 4f → check valve 4e. The pressure oil supplied to the valve 4a and led to the pipe line 11 via the switching valve 6 passes through the parallel passage → throttle → 5g → check valve 5f, and then passes through the right-hand travel direction switching valve 5a and the second direction switching valve. It is supplied to the arm directional control valve 5d through the parallel passage of group 5. Therefore, by appropriately selecting the throttles 4f and 5g, the flow rate of the pressure oil supplied to the arm directional control valve 5d can be controlled.

Further, the pressure oil of the second hydraulic pump 2 is switchably connected to the pipe line 12, and the pressure oil led to the pipe line 7 via the switching valve 6 is supplied to the left travel direction switching valve 4a.
The pressure oil led to the pipe line 12 is supplied to the right travel direction switching valve 5a. At this time, if the arm drive pressure<traveling drive pressure, the entire amount of the pressure oil of the first hydraulic pump 1 is supplied to the arm switching valve 5d, and the entire amount of the pressure oil of the second hydraulic pump 2 is supplied to the crawler which is the traveling body. Due to its inherent straight-line ability, it is evenly distributed to the left and right travel direction switching valves 4a and 5a (that is, the left and right travel motors), thereby maintaining straight-line travel ability.

Also, if arm drive pressure>travel drive pressure, throttle 4f,
5g to ensure the driving pressure for the arm and move the arm with the pressure oil from the first hydraulic pump 1. Excess oil other than the one used to move the arm is used by the left and right travel direction switching valves 4a and 5.
It is evenly distributed to A and maintains straight running performance.

Since the above-mentioned operation is the same for cases other than the arm, explanations for other actuators will be omitted.

In the embodiment shown in Fig. 2, an auxiliary switching valve is provided for all the directional switching valves in which all actuators are independent for running. Needless to say, in the case of an actuator without an auxiliary switching valve, the above-mentioned auxiliary switching valve may be omitted. Further, it goes without saying that the pilot circuit for automatically switching the switching valve 6 is not limited to the pilot circuit shown in FIG. 2, but may have other arrangements.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention. In the embodiment shown in FIG. 2, the switching valve 6 is configured to always maintain the "A" position by means of a spring force, and when an actuator that requires independence from running is activated while traveling straight, the switching valve 6 is In contrast, in the second embodiment shown in FIG. 3, pilot pressure is introduced to the pilot port and the switching valve 6 is switched to the ``ro'' position.On the contrary, in the second embodiment shown in FIG. The pilot pressure applied to the pilot port of the switching valve 6 is applied to the pilot port of the switching valve 6, and the pilot pressure applied to the pilot port of the switching valve 6 is zeroed out when the actuator that requires independence is activated while the vehicle is traveling straight. The difference is that the configuration of the pilot conduit and the auxiliary switching valve is changed so that the switching valve 6 is switched to the ``ro'' position by spring force.

(Operation of the second embodiment) At no load: In the state shown in FIG. It returns to the tank via the center bypass passage of group 4 of the first directional valve. Similarly, the pressure oil of the second hydraulic pump 2 is supplied to the switching valve 6.
via line 11 and returns to the tank via the center bypass passage of group 5 of the second directional valve. Further, since the pilot pipe line 15 is closed by the auxiliary switching valve 5a', the pressure oil of the pilot pump 13 is kept at the setting pressure of the relief valve 14 to maintain the switching valve 6 in the A position, and the excess oil is transferred to the relief valve 14.
and return to the tank.

When activated: A When traveling only in a straight line: Directional switching valve 4 for left travel
a to the A position (or B position) and the right travel direction switching valve 5a to the A position (or B position), the pressure oil of the pilot pump 13 flows from the pilot pipe 15 to the auxiliary switching valve 5a' to the pipe. Road 26
(pipe line 27) → auxiliary switching valve 4a' → pilot pipe 28, but the auxiliary switching valves 4b', 4
c', 5c', 5d' are all blocks (neutral position)
As a result, pilot pressure acts on the pilot port of the switching valve 6, and the switching valve 6 is held at the A position in FIG.

Therefore, the pressure oil of the first hydraulic pump 1 is distributed to the pipes 7 and 8, and the pressure oil led to the pipe 7 is directly led to the left travel directional control valve 4a and to the pipe 8. The pressurized oil is supplied to the left travel direction switching valve 4a via the parallel passage → throttle 4f → check valve 4e. That is, the entire amount of pressure oil from the first hydraulic pump 1 is supplied to the left travel motor.

Moreover, the pressure oil of the second hydraulic pump 2 is supplied to the pipes 11 and 1.
The pressure oil distributed to 2 and led to the pipe 11 goes through the parallel passage → throttle 5g → check valve 5f to the right-hand travel direction switching valve 5a, and the pressure oil led to the pipe 12 goes directly to the right-hand travel. It is supplied to the directional switching valve 5a. In other words, the entire amount of pressure oil from the second hydraulic pump 2 is supplied to the right travel motor.
If the first and second hydraulic pumps 1 and 2 have the same capacity, the vehicle will travel straight ahead.

B When operating other actuators that require independence during the above operation (while traveling straight) (for the sake of explanation, we will explain the operation when the arm is operated): Switch the arm directional control valve 5d while traveling straight. The auxiliary switching valve 5d' is also switched in conjunction with this, the pilot line 28 is connected to the drain line 29 (tank) via the auxiliary switching valve 5d', the pilot pressure becomes zero, and the switching valve 6 is operated by the spring force. automatically switches to the B position. Therefore, the first hydraulic pump 1 is switchably connected to the pipes 8 and 11, and the pressure oil led to the pipe 8 is routed from the parallel passage to the throttle 4f.
→ Left travel directional control valve 4 via check valve 4e
Pressure oil supplied to the pipe line 11 via the switching valve 6 is supplied to the right-hand direction switching valve 5a via the parallel passage → throttle 5g → check valve 5f, and the second direction switching valve 5a. It is supplied to the arm directional valve 5d via the parallel passage of valve group 5. At this time, by appropriately selecting the throttle amounts of the throttles 4f and 5g, the flow rate of the pressure oil supplied to the arm directional control valve 5d can be controlled.

Further, the second hydraulic pump 2 is connected to the pipes 7 and 12, and the pressure oil led to the pipe 7 is supplied to the left travel direction switching valve 4a, and the pressure oil led to the pipe 12 is supplied to the left travel direction switching valve 4a. Oil is supplied to the right travel direction switching valve 5a. At this time, if the arm drive pressure<traveling drive pressure, the entire amount of the pressure oil of the first hydraulic pump 1 is supplied to the arm switching valve 5d, and the entire amount of the pressure oil of the second hydraulic pump 2 is supplied to the crawler which is the traveling body. Due to the essential straight-line performance of the engine, the vehicle is equally distributed to the left and right travel direction switching valves 4a and 5a (that is, the left and right travel motors), resulting in straight-line travel performance.

Also, if arm drive pressure>travel drive pressure, throttle 4f,
5g to secure the drive pressure for the arm, and move the arm with the pressure oil from the first hydraulic pump 1, and the remaining excess oil is equally distributed to the left and right travel directional control valves 4a and 5a, ensuring straight-line travel performance. I can keep it. Since the above is the same for other actuators, explanations regarding other actuators will be omitted.

(Third Embodiment) The third embodiment shown in FIG.
In contrast to the second embodiment shown in FIG. 3 in which the switching valve 6 is automatically switched by pilot pressure, the switching valve 6 is operated according to the driver's will, that is, manually. It should be noted that the term "manual operation" refers to not only mechanical operation using a pedal or lever, but also electrical operation. Since the other basic configurations are the same as those in FIGS. 2 and 3, explanation of the operation will be omitted.

FIG. 5 shows the pipes 8 and 1 installed immediately before the switching valve 6 in the first to third embodiments of FIGS. 2 to 4.
2 is replaced with pipes 8' and 12' disposed immediately after the first hydraulic pump and the second hydraulic pump to provide the same function as the embodiment shown in FIGS. 2 to 4.

In addition, in the embodiments shown in FIGS. 2 to 5, the relief valves 9, 1
0 is installed between the switching valve 6 and the first and second hydraulic pumps, but the functions are the same even if the relief valves 9 and 10 are installed in the first and second directional switching valve groups 4 and 5, for example. be. In this way, the arrangement of the various valves is not limited to those shown in FIGS. 2 to 5.

(Effects of the Invention) Since the hydraulic circuit according to the present invention is configured as described above, even when various actuators are operated while traveling straight, if the switching valve is switched, the second (or first) The pressure oil of the first (or second) hydraulic pump is distributed equally to the left and right travel motors independently of other actuators, and the pressure oil of the first (or second) hydraulic pump is distributed to various actuators other than the travel motors for travel. Since it can be supplied with priority, there is no meandering even when traveling and connecting with other actuators at the same time.
It is possible to drive straight ahead. Furthermore, various actuators can be operated reliably, ensuring highly efficient work.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a conventional hydraulic excavator. FIG. 2 is a circuit diagram of a first embodiment of the present invention. FIG. 3 is a circuit diagram of the second embodiment. FIG. 4 is a circuit diagram of the third embodiment. FIG. 5 is a circuit diagram of another embodiment in which the piping in the vicinity of the switching valve 6 is changed. In the figure: 1...first hydraulic pump, 2...second hydraulic pump, 3...prime mover, 4...first directional switching valve group, 4a...left travel directional switching valve, 4b...bucket directional switching valve, 4c...first directional switching valve. Directional switching valve for 1 boom, 4a', 4b', 4c'... (interlocked with the directional switching valve)
Auxiliary switching valve, 4d... Relief valve, 4e... Check valve, 4f... Throttle, 5... Second directional switching valve group, 5a... Directional switching valve for right travel, 5b... Directional switching valve for second boom, 5c... For turning Directional switching valve, 5d
...Arm directional switching valve, 5a', 5c', 5d'...Auxiliary switching valve (interlocked with the directional switching valve), 5e...Relief valve, 5f...Check valve, 5g...throttle, 6...
Switching valve, 7, 8, 11, 12...pipe line, 9, 10...
Relief valve, 13... Pilot valve, 14... Relief valve, 15... Pilot pipe line, 16, 19,
25, 29...Drain pipe line, 17, 18, 20~
24, 26-28...Pilot conduit.

Claims (1)

[Scope of Claims] 1. A plurality of hydraulic pumps 1, 2, and 13, including at least first and second hydraulic pumps, and driven by these hydraulic pumps, consisting of the following constituent elements a) to d). a group 4 of first and second directional control valves comprising a plurality of actuators provided to the actuators; and a plurality of directional control valves that control the direction and flow rate of pressure oil supplied from the first and second hydraulic pumps to the actuators; A hydraulic circuit for a construction machine such as a hydraulic excavator, comprising: and 5, and a switching valve 6 for switching pressure oil supply lines from the first and second hydraulic pumps. (a) The first directional valve group 4 connects one of the left and right running directional valves 4a, a bucket directional valve 4b, a first boom directional valve 4c, etc. in parallel in random order. A throttle 4f and a check valve 4e are provided in series in the parallel passage connected to the travel directional control valve 4a, and a second directional control valve group 5 is provided.
Of the left and right, the other determined running direction switching valve 5a, second boom direction switching valve 5b, swinging direction switching valve 5c, and arm directional switching valve 5d
etc. are connected in parallel in random order, and narrowed down to a parallel passage connected to the traveling direction switching valve 5a.
5g and a check valve 5f were installed in series. (b) When the switching valve 6 is in the first state, the first hydraulic pump 1 is switched to one side of the travel mode via the most upstream main pressure oil inlet of the first directional switching valve group 4 and the switching valve 6. Between the valve 4a and the check valve 4e, the second hydraulic pump is connected between the other traveling directional valve 5a and the check valve 5f, and via the switching valve 6 to a group of second directional valves. 5 and the most upstream main pressure oil inlet. C. In the second state of the switching valve 6, the first hydraulic pump 1 is connected to the first directional switching valve group 4.
The second hydraulic pump 2 is also switched between the running directional switching valve 5a and the check valve 5f of the second directional switching valve group 5 through the main pressure oil inlet at the most upstream side and the switching valve 6. The valve 6 is switched to the main pressure oil inlet between the running directional control valve 4a of the first directional control valve group 4 and the check valve 4e and to the most upstream main pressure oil inlet of the second directional control valve group 5. Configured to connect. (d) The directional switching valves 4a, 5a for traveling are provided with auxiliary switching valves 4a', 5a' that are linked to the valves, and the directional switching valves 4b, 4c, 5c, 5d for actuators that require independence from traveling are provided. When auxiliary switching valves 4b', 4c', 5c', and 5d' are provided which operate in conjunction with the switching valves, and at least one actuator that requires running and independence is operated during straight-ahead running, the switching valve 6 is The pilot pressure is applied to the pilot port via the auxiliary switching valves 4b', 4c', 5c', and 5d, so that the switching valve 6 is automatically switched. 2. Each traveling directional switching valve 4a, 5a is provided with an auxiliary switching valve 4a', 5a' that interlocks with the valve, and the directional switching valve 4b, 4c, 5c, 5d for an actuator that requires independence from traveling is provided with an auxiliary switching valve 4a', 5a'. When auxiliary switching valves 4b', 4c', 5c', and 5d' are provided which operate in conjunction with the switching valves, and at least one actuator that requires running and independence is operated while traveling straight, the pilot of the switching valve 6 The pilot pressure acting on the port is reduced through the auxiliary switching valves 4b', 4c', 5c', and 5d', so that the switching valves are automatically switched. Range 1
Hydraulic circuit in construction machinery such as hydraulic excavator described in Section 2.